The present invention relates to high voltage contactors, and more particularly to an improved, synergistic system for supporting a magnetic field in the arc chute thereof.
Electrical contactors, as distinguished from circuit breakers, are not only called upon to interrupt load currents but also to institute such currents by making a circuit under load. Contactors do this repeatedly and regularly in order to start and stop electrical equipment on a routine basis. Hence the requirements, duty cycles, and construction of contactors differ markedly from circuit breakers, which are only called upon to operate under unusual circumstances, ordinarily when an overcurrent failure has occurred. Owing to the fact that circuit breakers operate only in the presence of high currents, breakers are known which utilize "linear" coils of conductors which provide a magnetic field adjacent the contacts for urging an arc into an arc chute for quenching. Other constructions are known, principally for lower current values, in which flux produced by a current-carrying coil is transferred to the appropriate arc chute area by means of magnetic pole pieces.
Unlike circuit breakers, contactors are ordinarily called upon to make and break operating-level currents, though on occasion higher currents must be dealt with. So-called air magnetic contactors of the high voltage variety necessarily make use of an arc chute for quenching the arc which is drawn upon interruption of heavy currents. Such arc chutes are conventionally used in conjunction with magnetic pole pieces and current-carrying coils which give rise to an arc-displacing magnetic field within the arc chute. This gives rise to occasional problems, however, in that the magnetic circuit has a tendency to saturate at high current levels which diminishes the capacity of the system to extinguish severe arcs. Conventionally this problem has been overcome by providing larger and thicker pole pieces.
With one type of contactor construction, load current is routed through conductors which extend along the tops of the arc chutes. The magnetic fields about these conductors tend to oppose, and therefore weaken, the magnetic field in the upper part of the arc chute which is produced by the pole pieces. To make matters worse, as current increases and produces a still stronger arc, the opposing magnetic field also increases and therefore diminshes the value of the arc-quenching field. It will therefore be understood that it would be highly advantageous to provide an improved magnetic circuit for high voltage contactors which eliminates difficulties with opposing flux fields, and encourages the movement of an arc into a quenching zone.
It is therefore an object of the present invention to provide a contactor assembly having improved arc extinguishing characteristics.
Another object is to provide an improved, synergistic magnetic circuit for a high voltage contactor.
Yet another object is to provide an improved magnetic circuit for a high voltage contactor which does not require the increased use of magnetic materials.
Yet another object is to provide a current routing system in an air-magnetic contactor which markedly improves the arc extinguishing capabilities thereof.